The present invention relates to an electrical connection device destined to be brought into contact with molten metal, for instance a bath of molten steel. Such devices are usually embedded in a metallurgical container with the purpose of continuously treating the metal therein by means of electrical energy. Such devices constitute, therefore, electrodes in contact at one end with a bath of molten material and assuring thereby the passage of an electric current which traverses the metal bath.
Among the metallurgical containers which are adapted to be equipped with such electrode, there are mentioned, in a non-restrictive way, tubs for the electrolysis of non-ferrous material, such as aluminum, or, in the field of treatment of ferrous metals treating containers to be maintained at a high temperature, or electrical furnaces, especially arc furnaces operated with direct current, and in the technical field somehow different from those mentioned, furnaces for heating and melting of glass.
One of the main problems encountered with such electrodes is the proper maintenance of its end portion which is in direct contact with the mass of molten metal and which is subjected at very high temperatures which, especially in the case of molten steel, may reach a temperature of 1800.degree. C. and even higher.
Certain of the known solutions for overcoming these problems consist in a modification of the geometry of the container of the furnace in such a manner to create locally a preferred location for the insertion of the electrode, in which the mass of molten metal is considerably less thermally aggressive than at the rest of the furnace (French Pat. Nos. 2,168,430, 2,276,388 and 2,285,044). However, these solutions require the permanent presence of a special formation of a bottom portion of the metal bath, which places certain restrictions on the use of the furnace.
Other known solutions prefer to place the electrode directly across the refractory wall at the bottom of the furnace and concentrate their effort in the cooling of the electrode. In this respect one may distinguish between constructions in which the electrode is equipped with an external or an internal cooling circuit. In the first case, for the reason of security, the cooling circuit is usually not placed in the refractory material at the bottom of the furnace, but at the outside of the furnace (French Pat. Nos. 1,538,996 and 2,292,367). However, the distance of the tip of the electrode from the cooling source is in this case the cause of the final disappearance, by melting, of an important part of the electrode, which increases the danger that the mass of molten material in the interior of the furnace may escape therefrom.
An external cooling system has also been already proposed which consists to form a protecting envelope about the electrode by means of a cooling fluid. The electrode is in this case not any longer in direct contact with the mass of molten material, which limits the choice of cooling fluid to one which consists of an electroconductive material.
The second above-mentioned case, to which also the present invention relates, is free of such restrictions since it is in this case possible to lead the cooling fluid directly to the neighborhood of the inner end of the electrode. Nevertheless, it is in this case highly desirable, and this is the aim of the present invention, to use cooling means of high performance. In the other case even a reduced wear at the inner end of the electrode entails the risk of destroying the refrigeration system by opening it up, which in turn may cause the introduction of the cooling fluid into the mass of molten material.